The invention relates in general to devices for dispensing liquid liner on the interior of rocket tubes and in particular to a device for dispensing a precise weight of liquid liner lengthwise into a rocket tube for subsequent dispersal. After the liner is dispensed, another apparatus, such as a brush, distributes the liner dispensed in the rocket tube.
Rocket motor tubes are lined with a fire retardant liner to prevent the propellant from burning through the tube wall. The liner is very viscous and must be metered in a precise amount. Too little liner results in inadequate motor protection during firing. Too much liner reduces the available volume for propellant thereby lowering the overall impulse of the rocket motor. One method of metering liner into the motor tube is with a pressure pot. The pressure pot is pressurized with air that forces liner out through a valve and a long tube that spans the length of the rocket tube. The valve is opened and a bead of liner is dispensed lengthwise in the rocket tube as the tube is moved axially along the discharge. After lining, the rocket tube's original weight is compared to the weight of the tube with the liner to determine the amount of liner dispensed in the tube. Liner is then added or subtracted to reach the desired liner weight. The rocket tubes are, for example, about three feet long and two to three inches in diameter. The dispensed liner is spread using a long flat blade. A spatula on a stick is used to add or remove liner.
Using the above-described method, it is difficult to dispense a precise amount of liner in the tube the first time. Moreover, as the liner gets thicker with time the rate at which the liner is dispensed varies. In addition, the method is very labor intensive. It is difficult to know how much liner is left in the pressure pot during the process. If the pressure pot runs empty, the liner will spit out thereby further complicating cleanup. After lining, cleanup of the pressure pot, flat blade spreader bar and surrounding area requires toluene to remove the liner from contaminated surfaces.
The present invention overcomes the problems of the prior art by providing an apparatus that can accurately meter the amount of liner dispensed in the tube. Using the invention, a user can remotely deposit a fixed weight of viscous liner material in a horizontal rocket tube using one hand to control both the amount of flow and the translation of the dispensing nozzle. After the weighed liner is dispensed in the tube, another apparatus (not part of the present invention) is used to spread the liner in the tube.
The invention will be better understood, and further objects, features, and advantages thereof will become more apparent from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings.